1. Field of the Invention
The present invention relates to a data determination method for a supplying-end module of an induction type power supply system and a related supplying-end module, and more particularly, to a supplying-end module of an induction type power supply system and a data determination method for the supplying-end module capable of obtaining modulation data from the receiving end.
2. Description of the Prior Art
For safety purposes, a power supply device of an induction type power supply system has to ensure that a proper power receiving device is positioned on the sensing area of a supplying-end coil of the power supply device, and that the power receiving device is ready to receive power before the power is supplied. In order to allow the power supply device to confirm the above conditions, a data code should be transmitted for identification purposes. The data code transmission is performed via the following steps: the power supply device drives the supplying-end coil to generate resonance and sends electromagnetic power to the power receiving device in order to transmit power. When the power receiving device receives the power, the power receiving device may change the impedance on the receiving-end coil via the signal modulation technology, and the variations are fed back to vary the amplitude of carriers on the supplying-end coil.
Wireless power standard Qi, which is a standard of short-distance wireless inductive power transmission developed by the Wireless Power Consortium (WPC), has a main purpose to provide a general and facilitating wireless charging for mobile devices and portable electronics. In a Qi system, a data format of universal asynchronous receiver transmitter (UART) is applied for data transmission, wherein the non-return-to-zero (NRZ) line code is utilized as the encoding scheme of data. According to the wireless power standard Qi, the clock frequency of the NRZ line code is 2 kilohertz (kHz); hence, the corresponding cycle is 0.5 millisecond (ms) and each cycle includes two sub-cycles with a length equal to 0.25 ms. The output data can be determined according to signal transition in the corresponding sub-cycles.
In general, the frequency of carrier signals on the coil of an induction type power supply system is substantially equal to 100-200 kHz; hence, the 2 kHz UART signals retrieved by the supplying end are first filtered by a low-pass filter circuit, and then demodulated via AC coupling and/or amplifying, in order to retrieve low frequency signals. This method has the following drawbacks. First, the low-pass filter is designed for a specific frequency, so its corresponding hardware circuit can only be utilized for the specific frequency. Presently the low-pass filter is designed based on the 2 kHz data format, and if another communication protocol is applied or the signal frequency changes afterward, this hardware circuit will not be utilized; this results in poor universality and flexibility. Second, the conventional demodulation technology requires the amplifications of voltage and current signals on the coil in the beginning, wherein the amplification ratio is fixed. When the signals enter the back end for further analyzing, small signals cannot be successfully analyzed if the amplification ratio is not large enough; and noises may easily be mixed into the signals if the amplification is too large. In addition, different from general wireless communication systems, the voltages and currents on the coil of the induction type power supply system may easily be influenced by the receiving-end loading. The dynamic load variations may influence the demodulation result and even cause a failed demodulation. Third, the conventional demodulation scheme has a poor performance in the wireless transmission when the transmitted power is large, because voltage variations on the coil may decrease with the increase in transmitted power, which results in lower signal determination capability and the allowed power is thereby limited. Fourth, the accuracy of each demodulation data can only be checked after the data is received. If any of the data bits is wrong, the data should be discarded, where the wrong data bits cannot be found out and corrected to the accurate data.
Thus, there is a need to provide a data determination method allowing the supplying-end module to effectively obtain the modulation data, in order to overcome the abovementioned problems.